What effect does a pH of 4.5-5.5 have on hair during the coloring process?

A pH level of 4.5 to 5.5 is considered to be slightly acidic and is beneficial for hair during the coloring process. At this pH range, the cuticle, which is the outermost layer of the hair, remains smooth and closed. This helps to secure the hair color within the hair shaft, resulting in better color retention. When the cuticle lays flat, it minimizes the amount of color that can be lost over time, leading to longer-lasting and vibrant hair color.

In contrast, a higher pH can open the cuticle, allowing color molecules to escape, which can lead to quicker fading of the color. This is why maintaining a pH within the 4.5 to 5.5 range is essential for optimal color retention in hair treatments.